Organic el element and solution containing organic el material

ABSTRACT

An organic electroluminescence device includes: an anode; a cathode; and an organic thin-film layer interposed between the anode and the cathode. The organic thin-film layer includes a phosphorescent-emitting layer containing a host and a phosphorescent dopant. The host contains a first host and a second host. The first host includes a substituted or unsubstituted polycyclic fused aromatic skeleton, the skeleton having 10 to 30 ring-forming atoms not including an atom of a substituent. The second host has an affinity level greater than the affinity level of the first host.

TECHNICAL FIELD

The present invention relates to an organic electroluminescence deviceand an organic-electroluminescent-material-containing solution.Especially, the invention relates to an organic electroluminescencedevice that includes a phosphorescent-emitting layer containing a hostand a phosphorescent dopant.

BACKGROUND ART

An organic electroluminescence device, which includes an organicemitting layer between an anode and a cathode, has been known to emitlight using exciton energy generated by a recombination of holes andelectrons that have been injected into the organic emitting layer.

Such an organic electroluminescence device, which has the advantages asa self-emitting device, is expected to serve as an emitting deviceexcellent in luminous efficiency, image quality, power consumption andthin design.

In order to use an emitting material in an organic electroluminescencedevice, a doping method for doping a dopant material in a host materialhas been known.

The doping method is designed so that excitons are efficiently generatedby the injected holes and electrons and exciton energy is efficientlyconverted into light emission, where the exciton energy generated by thehost is transferred to the dopant, so that light is emitted from thedopant.

Examples of a further improvement to be made in an organicelectroluminescence device include improvements in emission lifetime andluminous efficiency, to which various studies have been made.

For instance, in order to enhance internal quantum efficiency,developments have been made on a phosphorescent material that emitslight using triplet excitons. In recent years, there has been a reporton a phosphorescent organic electroluminescence device (see, forinstance, Patent Document 1).

With the use of such a phosphorescent material, 100% internal quantumefficiency can be theoretically achieved and an organicelectroluminescence device with high efficiency and low powerconsumption can be obtained.

In order to intermolecularly transfer the energy from a phosphorescenthost to a phosphorescent dopant (phosphorescent material) in aphosphorescent-emitting layer provided by doping the phosphorescentmaterial, triplet energy gap (referred to as Eg(T) hereinafter) of thephosphorescent host material is required to be larger than the Eg(T) ofthe phosphorescent dopant.

Typically known material that exhibits effectively large Eg(T) is CBP.

By using CBP as the phosphorescent host, energy can be transferred to aphosphorescent dopant for emitting light of a predetermined emittingwavelength (e.g., green, red), by which an emitting device of highefficiency that shows phosphorescent emission can be obtained.

However, although an organic electroluminescence device in which CBP isused as the phosphorescent host exhibits much higher luminous efficiencydue to phosphorescent emission, the organic electroluminescence devicehas such a short lifetime as to be practically inapplicable.

Accordingly, a material other than CBP that is usable as thephosphorescent host has been under development (see, for instance,non-Patent Document 1).

On the other hand, a variety of host materials for fluorescent dopantsare known. Various proposals have been made on a host material capableof, with a combination of a fluorescent dopant, exhibiting excellentluminous efficiency and lifetime.

However, though a fluorescent host has a greater singlet energy gapEg(S) than that of a fluorescent dopant, since the Eg(T) of thefluorescent host is not necessarily large, direct conversion of thefluorescent host to a phosphorescent host is not possible.

For instance, well-known examples of such a fluorescent host include ananthracene derivative, pylene derivative and naphthacene derivative.However, the Eg(T) of, for instance, an anthracene derivative isapproximately 1.9 eV, which is insufficient for obtaining emission ofvisible light wavelength from 450 nm to 750 nm and is thus not suitableas a phosphorescent host.

On the other hand, it is known that an organic electroluminescencedevice with a long lifetime and a high efficiency can be obtained withthe use of an emission layer containing a dopant in a host of aplurality of materials.

For instance, in Patent Document 2, a phosphorescent-emitting layer isprovided using a phosphorescent host containing two or morehole-transferring substances to improve the efficiency and lifetime.

-   [Patent Document 1] US2002/182441-   [Patent Document 2] JP-A-2006-135295-   [non-Patent Document 1] Applied Physics letters Vol. 90.123509    (2007)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Since the organic electroluminescence device disclosed in the PatentDocument 1 includes the phosphorescent-emitting layer, the organicelectroluminescence device exhibits high luminous efficiency and lowpower consumption. However, the lifetime of the organicelectroluminescence device is short.

In the non-Patent Document 1, though a variety of materials have beenstudied as a phosphorescent host, no such phosphorescent host that iscapable of efficiently transferring energy to a phosphorescent dopantand providing a phosphorescent-emitting layer that has a practicallylong lifetime has not been found.

The organic electroluminescence device according to Patent Document 2exhibits an emission with long lifetime and high efficiency with the useof a phosphorescent host of a plurality of materials. However, since thematerial constituting the phosphorescent host is CBP or a compoundsimilar to CBP, the effect is not sufficient.

An object of the invention is to provide a phosphorescent-emittingorganic electroluminescence device with a high efficiency and longlifetime and an organic-electroluminescent-material-containing solution.

Means for Solving the Problems

An organic electroluminescence device according to an aspect of theinvention includes: an anode; a cathode; and an organic thin-film layerinterposed between the anode and the cathode, in which the organicthin-film layer includes a phosphorescent-emitting layer containing ahost and a phosphorescent dopant, the host contains a first host and asecond host, one of the first host and the second host exhibits a higheraffinity level than the other, and at least one of the first host andthe second host includes a substituted or unsubstituted polycyclic fusedaromatic skeleton, the skeleton having 10 to 30 ring-forming atoms notincluding an atom of a substituent.

In the above aspect of the invention, a phosphorescent dopant is addedto the host including the first host and the second host to provide aphosphorescent-emitting layer.

The phosphorescent dopant is provided by a material that emitsphosphorescent light by receiving energy from the host or a materialthat emits light by generating triplet excitons directly thereon.

In the above aspect of the invention, the stability of the molecule canbe enhanced and the emission lifetime can be lengthened by providing atleast one of the skeletons of the first and the second hosts by apolycyclic fused aromatic compound.

At this time, since the stability of the molecule is not sufficientlyenhanced when there are too small number of ring-forming atoms (notcounting atom(s) of substituent(s)) in the polycyclic fused aromaticskeleton, the ring-forming atoms (not counting atom(s) ofsubstituent(s)) in the polycyclic fused aromatic skeleton are 10 ormore.

On the other hand, when the ring number of the polycyclic fused aromaticskeleton is too much, HOMO-LUMO gap becomes too narrow to reduce theEg(T). In this case, the energy transfer to the phosphorescent dopantthat causes a phosphorescent emission of useful wavelength cannot beobtained. Accordingly, the ring-forming atoms (not counting atom(s) ofsubstituent(s)) in the polycyclic fused aromatic skeleton are 30 orless.

Incidentally, the ring-forming atoms (not counting atom(s) ofsubstituent(s)) in the polycyclic fused aromatic skeleton are favorablyin a range from 15 to 30, more favorably 20 to 30.

However, when the host is provided only by the polycyclic fused aromaticcompound, the following problem arises.

As described above, the host having the polycyclic fused aromaticskeleton has a large Eg(T), so that the energy transfer from the host tothe phosphorescent dopant can be secured.

Generally speaking, a material that exhibits a large Eg(T) shows smallaffinity level (referred to as Af hereinafter).

Accordingly, when the host is provided solely by a polycyclic fusedaromatic compound, the reduced Af prohibits the electron injection tothe host. Consequently, the drive voltage of the organicelectroluminescence device increases to lower the luminous efficiency.Further, the recombination of hole and electron may be concentrated to aside adjacent to the cathode of the emitting layer to reduce theemission lifetime.

In contrast, the host includes the first host and the second host in theabove aspect of the invention. Since the first host and the second hostare provided by different materials, there is a difference in therespective Af, where the Af of one of the first and the second hosts islarger than the Af of the other.

According to the above arrangement, since the electrons from the cathodeare injected into one of the hosts with larger Af, the increase in thedrive voltage of the organic electroluminescence device andconcentration of electron recombination to the side of the cathode canbe avoided, so that the decrease in luminous efficiency and emissionlifetime can be prevented.

Incidentally, metal complexes containing Al, Zn, Ga, Be and the like mayalternatively be used as the host in addition to the polycyclic fusedaromatic compound. Examples of the metal complexes are BAlq andZn(BTP)₂.

In the above aspect of the invention, the first host preferably has asubstituted or unsubstituted polycyclic fused aromatic skeleton of 10 to30 ring-forming atoms (not counting atom(s) of substituent(s)), and anaffinity level of the second host is preferably greater than theaffinity level of the first host.

According to the above arrangement, since the electrons from the cathodeare injected into the second host with larger Af, the increase in thedrive voltage of the organic electroluminescence device andconcentration of electron recombination to the side of the cathode canbe avoided, so that the decrease in luminous efficiency and emissionlifetime can be prevented.

In the above aspect of the invention, since the first host and thesecond host are contained in a single organic layer, a devicepreparation time can be reduced as compared with a double-layerstructure of the first and the second hosts. Specifically, when thelayer is provided in-line, since the layer preparation time of therespective layers has to be synchronized, increase in the number oflayers results in increase in preparation time. On the other hand,though the rate control of respective vapor deposition sources duringlayer formation becomes difficult in a single layer structure, thedevice preparation time can be reduced.

It should be noted that a “fluorescent host” and a “phosphorescent host”herein respectively mean a host material combined with a fluorescentdopant and a host material combined with a phosphorescent dopant, andthat a distinction between the fluorescent host and phosphorescent hostis not unambiguously derived only from a molecular structure of the hostin a limited manner.

In other words, the fluorescent host herein means a material for forminga fluorescent-emitting layer containing a fluorescent dopant, and doesnot mean a host that is only usable as a host of a fluorescent material.Likewise, the phosphorescent host herein means a material for forming aphosphorescent-emitting layer containing a phosphorescent dopant, anddoes not mean a host that is only usable as a host of a phosphorescentmaterial.

The affinity level Af (electron affinity) means energy emitted orabsorbed when an electron is fed to a molecule of a material. Theaffinity level is defined as “positive” when energy is emitted whilebeing defined as “negative” when energy is absorbed.

The affinity level Af is defined by an ionization potential Ip and anoptical energy gap Eg(S) as follows.Af=Ip−Eg(S)

Here, the ionization potential Ip refers to energy necessary for acompound of each material to remove electrons to ionize, for which avalue measured with an ultraviolet ray photoelectron spectrometer (AC-3manufactured by Riken Keiki Co., Ltd.).

The optical energy gap Eg(S) refers to a difference between a conductionlevel and a valence electron level. For instance, Eg(S) is a valueobtained by converting into energy a wavelength value at an intersectionof a long-wavelength-side tangent line in an absorbing spectrum of atoluene-diluted solution of each material and a base line in theabsorbing spectrum obtained according to absorbance.

In the above aspect of the invention, the first host preferably has thepolycyclic fused aromatic skeleton, and a minimum excited triplet energygap of the first host is in a range from 2.1 eV to 2.7 eV.

Since the Eg(T) of the first host is in a range from 2.1 eV to 2.7 eV,the energy can be transferred to a phosphorescent dopant of which Eg(T)is 2.7 eV or less, more efficiently 2.5 eV or less to cause aphosphorescent emission.

While an anthracene derivative, which is well-known as a fluorescenthost, is not suitably applied as a host for red-emitting phosphorescentdopant, the first host according to the invention, of which the Eg(T) is2.1 eV or more, can be effectively applied for the red-emittingphosphorescent dopant to emit light.

However, while CBP, which is a conventionally-known phosphorescent host,can serve as the host even for a phosphorescent dopant for emittinglight of a shorter wavelength than green, the first host according tothe invention with the Eg(T) of 2.7 eV or less can be used for agreen-emitting phosphorescent dopant but cannot be used for aphosphorescent dopant for emitting light of a shorter wavelength thangreen.

Traditionally, the host material is selected in terms of wideapplication to a variety of phosphorescent dopants ranging from aphosphorescent dopant that exhibits blue phosphorescent emission to aphosphorescent dopant that exhibits red phosphorescent emission.Accordingly, CBP and the like that exhibit a large Eg(T) has been usedas a host.

However, though the Eg(T) of CBP is large, the emission lifetime isshortened.

In this respect, since the ring-forming atoms (not counting atom(s) ofsubstituent(s)) of the polycyclic fused aromatic skeleton is in a rangefrom 10 to 30 and the Eg(T) is in a range from 2.1 eV to 2.7 eV in theabove aspect of the invention, though the compound is not applicable asa host for blue light (i.e. with wide gap), the compound serves as ahost for a phosphorescent dopant of 2.7 eV or less.

Further, when the Eg(T) is too large as is exhibited by CBP, thedifference between the Eg(T) of the phosphorescent dopant and the Eg(T)of the host to a red-emitting phosphorescent dopant becomes too large toprohibit an efficient intermolecular energy transfer.

On the other hand, since the Eg(T) of the first host of the invention issuitable for a red-emitting phosphorescent dopant, the energy can beefficiently transferred from the host to the phosphorescent dopant, thusproviding an extremely efficient phosphorescent-emitting layer.

The Eg(T) of a material is defined based on, for instance, aphosphorescence spectrum.

The Eg(T) may be exemplarily defined as follows.

Specifically, each material is dissolved in an EPA solvent(diethylether:isopentane:ethanol=5:5:2 in volume ratio) at aconcentration of 10 μmol/L, thereby forming a sample for phosphorescencemeasurement.

The sample for phosphorescence measurement is put into a quartz cell andis cooled to 77 K.

Excitation light is irradiated to the sample and the wavelength ofemitted phosphorescence is measured.

A tangent line is drawn to be tangent to a rising section adjacent toshort-wavelength of the obtained phosphorescence spectrum, a wavelengthvalue at an intersection of the tangent line and a base line obtainedfrom absorbance is obtained.

The value of the obtained wavelength value converted into energy isdefined as the Eg(T).

For the measurement, for instance, a commercially-available measuringequipment F-4500 (manufactured by Hitachi, Ltd.) may be used.

However, the Eg(T) does not need to be defined by the above method, butmay be defined by any other suitable method as long as such a method iscompatible with the invention.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is present in a chemical structure formula as a divalent ormultivalent group.

Examples of the substituent for the polycyclic fused aromatic skeletonare halogen atom, hydroxyl group, substituted or unsubstituted aminogroup, nitro group, cyano group, substituted or unsubstituted alkylgroup, substituted or unsubstituted alkenyl group, substituted orunsubstituted cycloalkyl group, substituted or unsubstituted alkoxygroup, substituted or unsubstituted aromatic hydrocarbon group,substituted or unsubstituted aromatic heterocyclic group, substituted orunsubstituted aralkyl group, substituted or unsubstituted aryloxy group,substituted or unsubstituted alkoxycarbonyl group, and carboxyl group.

When the polycyclic fused aromatic skeleton includes a plurality ofsubstituents, the substituents may form a ring.

Examples of the halogen atom are fluorine, chlorine, bromine and iodine.

The substituted or unsubstituted amino group is represented by —NX¹X².X¹ and X² each independently and exemplarily represent a hydrogen atom,methyl group, ethyl group, propyl group, isopropyl group, n-butyl group,s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexylgroup, n-heptyl group, n-octyl group, hydroxymethyl group,1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutyl group,1,2-dihydroxyethyl group, 1,3-dihydroxyisopropyl group,2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethylgroup, 1-chloroethyl group, 2-chloroethyl group, 2-chloroisobutyl group,1,2-dichloroethyl group, 1,3-dichloroisopropyl group,2,3-dichloro-t-butyl group, 1,2,3-trichloropropyl group, bromomethylgroup, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group,1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo-t-butylgroup, 1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group, 1,2,3-trinitropropyl group, phenylgroup, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 2-anthrylgroup, 9-anthryl group, 1-phenanthryl group, 2-phenanthryl group,3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group,1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group,4-styrylphenyl group, 1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group,2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group,p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-terphenyl-2-yl group,m-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group,o-tolyl group, m-tolyl group, p-tolyl group, p-t-butylphenyl group,p-(2-phenylpropyl)phenyl group, 3-methyl-2-naphthyl group,4-methyl-1-naphthyl group, 4-methyl-1-anthryl group, 4′-methylbiphenylylgroup, 4″-t-butyl-p-terphenyl-4-yl group, 2-pyrrolyl group, 3-pyrrolylgroup, pyrazinyl group, 2-pyridinyl group, 3-pyridinyl group,4-pyridinyl group, 2-indolyl group, 3-indolyl group, 4-indolyl group,5-indolyl group, 6-indolyl group, 7-indolyl group, 1-isoindolyl group,3-isoindolyl group, 4-isoindolyl group, 5-isoindolyl group, 6-isoindolylgroup, 7-isoindolyl group, 2-furyl group, 3-furyl group, 2-benzofuranylgroup, 3-benzofuranyl group, 4-benzofuranyl group, 5-benzofuranyl group,6-benzofuranyl group, 7-benzofuranyl group, 1-isobenzofuranyl group,3-isobenzofuranyl group, 4-isobenzofuranyl group, 5-isobenzofuranylgroup, 6-isobenzofuranyl group, 7-isobenzofuranyl group, 2-quinolylgroup, 3-quinolyl group, 4-quinolyl group, 5-quinolyl group, 6-quinolylgroup, 7-quinolyl group, 8-quinolyl group, 1-isoquinolyl group,3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group,6-isoquinolyl group, 7-isoquinolyl group, 8-isoquinolyl group,2-quinoxalinyl group, 5-quinoxalinyl group, 6-quinoxalinyl group,1-phenanthridinyl group, 2-phenanthridinyl group, 3-phenanthridinylgroup, 4-phenanthridinyl group, 6-phenanthridinyl group,7-phenanthridinyl group, 8-phenanthridinyl group, 9-phenanthridinylgroup, 10-phenanthridinyl group, 1-acridinyl group, 2-acridinyl group,3-acridinyl group, 4-acridinyl group, 9-acridinyl group,1,7-phenanthroline-2-yl group, 1,7-phenanthroline-3-yl group,1,7-phenanthroline-4-yl group, 1,7-phenanthroline-5-yl group,1,7-phenanthroline-6-yl group, 1,7-phenanthroline-8-yl group,1,7-phenanthroline-9-yl group, 1,7-phenanthroline-10-yl group,1,8-phenanthroline-2-yl group, 1,8-phenanthroline-3-yl group,1,8-phenanthroline-4-yl group, 1,8-phenanthroline-5-yl group,1,8-phenanthroline-6-yl group, 1,8-phenanthroline-7-yl group,1,8-phenanthroline-9-yl group, 1,8-phenanthroline-10-yl group,1,9-phenanthroline-2-yl group, 1,9-phenanthroline-3-yl group,1,9-phenanthroline-4-yl group, 1,9-phenanthroline-5-yl group,1,9-phenanthroline-6-yl group, 1,9-phenanthroline-7-yl group,1,9-phenanthroline-8-yl group, 1,9-phenanthroline-10-yl group,1,10-phenanthroline-2-yl group, 1,10-phenanthroline-3-yl group,1,10-phenanthroline-4-yl group, 1,10-phenanthroline-5-yl group,2,9-phenanthroline-1-yl group, 2,9-phenanthroline-3-yl group,2,9-phenanthroline-4-yl group, 2,9-phenanthroline-5-yl group,2,9-phenanthroline-6-yl group, 2,9-phenanthroline-7-yl group,2,9-phenanthroline-8-yl group, 2,9-phenanthroline-10-yl group,2,8-phenanthroline-1-yl group, 2,8-phenanthroline-3-yl group,2,8-phenanthroline-4-yl group, 2,8-phenanthroline-5-yl group,2,8-phenanthroline-6-yl group, 2,8-phenanthroline-7-yl group,2,8-phenanthroline-9-yl group, 2,8-phenanthroline-10-yl group,2,7-phenanthroline-1-yl group, 2,7-phenanthroline-3-yl group,2,7-phenanthroline-4-yl group, 2,7-phenanthroline-5-yl group,2,7-phenanthroline-6-yl group, 2,7-phenanthroline-8-yl group,2,7-phenanthroline-9-yl group, 2,7-phenanthroline-10-yl group,1-phenazinyl group, 2-phenazinyl group, 1-phenothiazinyl group,2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group,1-phenoxazinyl group, 2-phenoxazinyl group, 3-phenoxazinyl group,4-phenoxazinyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolylgroup, 2-oxadiazolyl group, 5-oxadiazolyl group, 3-furazanyl group,2-thienyl group, 3-thienyl group, 2-methylpyrrol-1-yl group,2-methylpyrrol-3-yl group, 2-methylpyrrol-4-yl group,2-methylpyrrol-5-yl group, 3-methylpyrrol-1-yl group,3-methylpyrrol-2-yl group, 3-methylpyrrol-4-yl group,3-methylpyrrol-5-yl group, 2-t-butylpyrrol-4-yl group,3-(2-phenylpropyl)pyrrol-1-yl group, 2-methyl-1-indolyl group,4-methyl-1-indolyl group, 2-methyl-3-indolyl group, 4-methyl-3-indolylgroup, 2-t-butyl-1-indolyl group, 4-t-butyl-1-indolyl group,2-t-butyl-3-indolyl group, and 4-t-butyl-3-indolyl group.

Examples of the substituted or unsubstituted alkyl group are methylgroup, ethyl group, propyl group, isopropyl group, n-butyl group,s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexylgroup, n-heptyl group, n-octyl group, hydroxymethyl group,1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutyl group,1,2-dihydroxyethyl group, 1,3-dihydroxyisopropyl group,2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethylgroup, 1-chloroethyl group, 2-chloroethyl group, 2-chloroisobutyl group,1,2-dichloroethyl group, 1,3-dichloroisopropyl group,2,3-dichloro-t-butyl group, 1,2,3-trichloropropyl group, bromomethylgroup, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group,1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo-t-butylgroup, 1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group, and 1,2,3-trinitropropyl group.

Examples of the substituted or unsubstituted alkenyl group are vinylgroup, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group,1,3-butanedienyl group, 1-methylvinyl group, styryl group,4-diphenylaminostyryl group, 4-di-p-tolylaminostyryl group,4-di-m-tolylaminostyryl group, 2,2-diphenylvinyl group,1,2-diphenylvinyl group, 1-methylallyl group, 1,1-dimethylallyl group,2-methylallyl group, 1-phenylallyl group, 2-phenylallyl group,3-phenylallyl group, 3,3-diphenylallyl group, 1,2-dimethylallyl group,1-phenyl-1-butenyl group, and 3-phenyl-1-butenyl group.

Examples of the substituted or unsubstituted cycloalkyl group arecyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexylgroup, and 4-methylcyclohexyl group.

The substituted or unsubstituted alkoxy group is represented by —OY.Examples of Y are methyl group, ethyl group, propyl group, isopropylgroup, n-butyl group, s-butyl group, isobutyl group, t-butyl group,n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group,hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group,2-hydroxyisobutyl group, 1,2-dihydroxyethyl group,1,3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group,1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group,2-chloroethyl group, 2-chloroisobutyl group, 1,2-dichloroethyl group,1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group,1,2,3-trichloropropyl group, bromomethyl group, 1-bromoethyl group,2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group,1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl group,1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group, and 1,2,3-trinitropropyl group.

Examples of the substituted or unsubstituted aromatic hydrocarbon groupare a phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group,2-anthryl group, 9-anthryl group, 1-phenanthryl group, 2-phenanthrylgroup, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group,1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group,1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group, 2-biphenylyl group,3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group,p-terphenyl-3-yl group, p-terphenyl-2-yl group, m-terphenyl-4-yl group,m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, m-tolylgroup, p-tolyl group, p-t-butylphenyl group, p-(2-phenylpropyl)phenylgroup, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group,4-methyl-1-anthryl group, 4′-methylbiphenylyl group, and4″-t-butyl-p-terphenyl-4-yl group.

Examples of the substituted or unsubstituted heterocyclic group are a1-pyroryl group, 2-pyroryl group, 3-pyroryl group, pyrazinyl group,2-pyridiny group, 3-pyridinyl group, 4-pyridinyl group, 1-indolyl group,2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group,6-indolyl group, 7-indolyl group, 1-isoindolyl group, 2-isoindolylgroup, 3-isoindolyl group, 4-isoindolyl group, 5-isoindolyl group,6-isoindolyl group, 7-isoindolyl group, 2-furyl group, 3-furyl group,2-benzofuranyl group, 3-benzofuranyl group, 4-benzofuranyl group,5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group,1-isobenzofuranyl group, 3-isobenzofuranyl group, 4-isobenzofuranylgroup, 5-isobenzofuranyl group, 6-isobenzofuranyl group,7-isobenzofuranyl group, quinolyl group, 3-quinolyl group, 4-quinolylgroup, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8-quinolylgroup, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group,5-isoquinolyl group, 6-isoquinolyl group, 7-isoquinolyl group,8-isoquinolyl group, 2-quinoxalinyl group, 5-quinoxalinyl group,6-quinoxalinyl group, 1-phenanthrydinyl group, 2-phenanthrydinyl group,3-phenanthrydinyl group, 4-phenanthrydinyl group, 6-phenanthrydinylgroup, 7-phenanthrydinyl group, 8-phenanthrydinyl group,9-phenanthrydinyl group, 10-phenanthrydinyl group, 1-acridinyl group,2-acridinyl group, 3-acridinyl group, 4-acridinyl group, 9-acridinylgroup, 1,7-phenanthroline-2-yl group, 1,7-phenanthroline-3-yl group,1,7-phenanthroline-4-yl group, 1,7-phenanthroline-5-yl group,1,7-phenanthroline-6-yl group, 1,7-phenanthroline-8-yl group,1,7-phenanthroline-9-yl group, 1,7-phenanthroline-10-yl group,1,8-phenanthroline-2-yl group, 1,8-phenanthroline-3-yl group,1,8-phenanthroline-4-yl group, 1,8-phenanthroline-5-yl group,1,8-phenanthroline-6-yl group, 1,8-phenanthroline-7-yl group,1,8-phenanthroline-9-yl group, 1,8-phenanthroline-10-yl group,1,9-phenanthroline-2-yl group, 1,9-phenanthroline-3-yl group,1,9-phenanthroline-4-yl group, 1,9-phenanthroline-5-yl group,1,9-phenanthroline-6-yl group, 1,9-phenanthroline-7-yl group,1,9-phenanthroline-8-yl group, 1,9-phenanthroline-10-yl group,1,10-phenanthroline-2-yl group, 1,10-phenanthro line-3-yl group,1,10-phenanthroline-4-yl group, 1,10-phenanthroline-5-yl group,2,9-phenanthroline-1-yl group, 2,9-phenanthroline-3-yl group,2,9-phenanthroline-4-yl group, 2,9-phenanthroline-5-yl group,2,9-phenanthroline-6-yl group, 2,9-phenanthroline-7-yl group,2,9-phenanthroline-8-yl group, 2,9-phenanthroline-10-yl group,2,8-phenanthroline-1-yl group, 2,8-phenanthroline-3-yl group,2,8-phenanthroline-4-yl group, 2,8-phenanthroline-5-yl group,2,8-phenanthroline-6-yl group, 2,8-phenanthroline-7-yl group,2,8-phenanthroline-9-yl group, 2,8-phenanthroline-10-yl group,2,7-phenanthroline-1-yl group, 2,7-phenanthroline-3-yl group,2,7-phenanthroline-4-yl group, 2,7-phenanthroline-5-yl group,2,7-phenanthroline-6-yl group, 2,7-phenanthroline-8-yl group,2,7-phenanthroline-9-yl group, 2,7-phenanthroline-10-yl group,1-phenazinyl group, 2-phenazinyl group, 1-phenothiazinyl group,2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group,10-phenothiazinyl group, -1-phenoxazinyl group, 2-phenoxazinyl group,3-phenoxazinyl group, 4-phenoxazinyl group, 10-phenoxazinyl group,2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-oxadiazolylgroup, 5-oxadiazolyl group, 3-furazanyl group, 2-thienyl group,3-thienyl group, 2-methylpyrrole-1-yl group, 2-methylpyrrole-3-yl group,2-methylpyrrole-4-yl group, 2-methylpyrrole-5-yl group,3-methylpyrrole-1-yl group, 3-methylpyrrole-2-yl group,3-methylpyrrole-4-yl group, 3-methylpyrrole-5-yl group,2-t-butylpyrrole-3-yl group, -3-(2-phenylpropyl)pyrrole-1-yl group,2-methyl-1-indolyl group, 4-methyl-1-indolyl group, 2-methyl-3-indolylgroup, 4-methyl-3-indolyl group, 2-t-butyl-1-indolyl group,4-t-butyl-1-indolyl group, 2-t-butyl-3-indolyl group,4-t-butyl-3-indolyl group and the like.

Examples of the substituted or unsubstituted aralkyl group are a benzylgroup, 1-phenylethyl group, 2-phenylethyl group, 1-phenylisopropylgroup, 2-phenylisopropyl group, phenyl-t-butyl group, α-naphthylmethylgroup, 1-α-naphthylethyl group, 2-α-naphthylethyl group,1-α-naphthylisopropyl group, 2-α-naphthylisopropyl group,β-naphthylmethyl group, 1-β-naphthylethyl group, 2-β-naphthylethylgroup, 1-β-naphthylisopropyl group, 2-β-naphthylisopropyl group,1-pyrorylmethyl group, 2-(1-pyroryl)ethyl group, p-methylbenzyl group,m-methylbenzyl group, o-methylbenzyl group, p-chlorobenzyl group,m-chlorobenzyl group, o-chlorobenzyl group, p-bromobenzyl group,m-bromobenzyl group, o-bromobenzyl group, p-iodobenzyl group,m-iodobenzyl group, o-iodobenzyl group, p-hydroxybenzyl group,m-hydroxybenzyl group, o-hydroxybenzyl group, p-aminobenzyl group,m-aminobenzyl group, o-aminobenzyl group, p-nitrobenzyl group,m-nitrobenzyl group, o-nitrobenzyl group, p-cyanobenzyl group,m-cyanobenzyl group, o-cyanobenzyl group, 1-hydroxy-2-phenylisopropylgroup and 1-chloro-2-phenylisopropyl group.

The substituted or unsubstituted aryloxy group is represented by —OZ.Examples of Z include a phenyl group, a 1-naphthyl group, a 2-naphthylgroup, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a4-phenanthryl group, a 9-phenanthryl group, a 1-naphthacenyl group, a2-naphthacenyl group, a 9-naphthacenyl group, a 1-pyrenyl group, a2-pyrenyl group, a 4-pyrenyl group, a 2-biphenylyl group, a 3-biphenylylgroup, a 4-biphenylyl group, a p-terphenyl-4-yl group, ap-terphenyl-3-yl group, a p-terphenyl-2-yl group, an m-terphenyl-4-ylgroup, an m-terphenyl-3-yl group, an m-terphenyl-2-yl group, an o-tolylgroup, an m-tolyl group, a p-tolyl group, a p-t-butylphenyl group, ap-(2-phenylpropyl)phenyl group, a 3-methyl-2-naphthyl group, a4-methyl-1-naphthyl group, a 4-methyl-1-anthryl group, a4′-methylbiphenylyl group, a 4″-t-butyl-p-terphenyl-4-yl group, a2-pyrrolyl group, a 3-pyrrolyl group, a pyrazinyl group, a 2-pyrizinylgroup, a 3-pyrizinyl group, a 4-pyrizinyl group, a 2-indolyl group, a3-indolyl group, a 4-indolyl group, a 5-indolyl group, a 6-indolylgroup, a 7-indolyl group, a 1-isoindolyl group, a 3-isoindolyl group, a4-isoindolyl group, a 5-isoindolyl group, a 6-isoindolyl group, a7-isoindolyl group, a 2-furyl group, a 3-furyl group, a 2-benzofuranylgroup, a 3-benzofuranyl group, a 4-benzofuranyl group, a 5-benzofuranylgroup, a 6-benzofuranyl group, a 7-benzofuranyl group, a1-isobenzofuranyl group, a 3-isobenzofuranyl group, a 4-isobenzofuranylgroup, a 5-isobenzofuranyl group, a 6-isobenzofuranyl group, a7-isobenzofuranyl group, a 2-quinolyl group, a 3-quinolyl group, a4-quinolyl group, a 5-quinolyl group, a 6-quinolyl group, a 7-quinolylgroup, a 8-quinolyl group, a 1-isoquinolyl group, a 3-isoquinolyl group,a 4-isoquinolyl group, a 5-isoquinolyl group, a 6-isoquinolyl group, a7-isoquinolyl group, a 8-isoquinolyl group, a 2-quinoxalinyl group, a5-quinoxalinyl group, a 6-quinoxalinyl group, a 1-phenanthridinyl group,a 2-phenanthridinyl group, a 3-phenanthridinyl group, a4-phenanthridinyl group, a 6-phenanthridinyl group, a 7-phenanthridinylgroup, a 8-phenanthridinyl group, a 9-phenanthridinyl group, a10-phenanthridinyl group, a 1-acridinyl group, a 2-acridinyl group, a3-acridinyl group, a 4-acridinyl group, a 9-acridinyl group, a1,7-phenanthroline-2-yl group, a 1,7-phenanthroline-3-yl group, a1,7-phenanthroline-4-yl group, a 1,7-phenanthroline-5-yl group, a1,7-phenanthroline-6-yl group, a 1,7-phenanthroline-8-yl group, a1,7-phenanthroline-9-yl group, a 1,7-phenanthroline-10-yl group, a1,8-phenanthroline-2-yl group, a 1,8-phenanthroline-3-yl group, a1,8-phenanthroline-4-yl group, a 1,8-phenanthroline-5-yl group, a1,8-phenanthroline-6-yl group, a 1,8-phenanthroline-7-yl group, a1,8-phenanthroline-9-yl group, a 1,8-phenanthroline-10-yl group, a1,9-phenanthroline-2-yl group, a 1,9-phenanthroline-3-yl group, a1,9-phenanthroline-4-yl group, a 1,9-phenanthroline-5-yl group, a1,9-phenanthroline-6-yl group, a 1,9-phenanthroline-7-yl group, a1,9-phenanthroline-8-yl group, a 1,9-phenanthroline-10-yl group, a1,10-phenanthroline-2-yl group, a 1,10-phenanthroline-3-yl group, a1,10-phenanthroline-4-yl group, a 1,10-phenanthroline-5-yl group, a2,9-phenanthroline-1-yl group, a 2,9-phenanthroline-3-yl group, a2,9-phenanthroline-4-yl group, a 2,9-phenanthroline-5-yl group, a2,9-phenanthroline-6-yl group, a 2,9-phenanthroline-7-yl group, a2,9-phenanthroline-8-yl group, a 2,9-phenanthroline-10-yl group, a2,8-phenanthroline-1-yl group, a 2,8-phenanthroline-3-yl group, a2,8-phenanthroline-4-yl group, a 2,8-phenanthroline-5-yl group, a2,8-phenanthroline-6-yl group, a 2,8-phenanthroline-7-yl group, a2,8-phenanthroline-9-yl group, a 2,8-phenanthroline-10-yl group, a2,7-phenanthroline-1-yl group, a 2,7-phenanthroline-3-yl group, a2,7-phenanthroline-4-yl group, a 2,7-phenanthroline-5-yl group, a2,7-phenanthroline-6-yl group, a 2,7-phenanthroline-8-yl group, a2,7-phenanthroline-9-yl group, a 2,7-phenanthroline-10-yl group, a1-phenazinyl group, a 2-phenazinyl group, a 1-phenothiazinyl group, a2-phenothiazinyl group, a 3-phenothiazinyl group, a 4-phenothiazinylgroup, a 1-phenoxazinyl group, a 2-phenoxazinyl group, a 3-phenoxazinylgroup, a 4-phenoxazinyl group, a 2-oxazolyl group, a 4-oxazolyl group, a5-oxazolyl group, a 2-oxadiazolyl group, a 5-oxadiazolyl group, a3-furazanyl group, a 2-thienyl group, a 3-thienyl group, a2-methylpyrrol-1-yl group, a 2-methylpyrrol-3-yl group, a2-methylpyrrol-4-yl group, a 2-methylpyrrol-5-yl group, a3-methylpyrrol-1-yl group, a 3-methylpyrrol-2-yl group, a3-methylpyrrol-4-yl group, a 3-methylpyrrol-5-yl group, a2-t-butylpyrrol-4-yl group, a 3-(2-phenylpropyl)pyrrol-1-yl group, a2-methyl-1-indolyl group, a 4-methyl-1-indolyl group, a2-methyl-3-indolyl group, a 4-methyl-3-indolyl group, a2-t-butyl-1-indolyl group, a 4-t-butyl-1-indolyl group, a2-t-butyl-3-indolyl group, and a 4-t-butyl-3-indolyl group.

The substituted or unsubstituted alkoxycarbonyl group are represented as—COOY. Examples of Y are methyl group, ethyl group, propyl group,isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butylgroup, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group,hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group,2-hydroxyisobutyl group, 1,2-dihydroxyethyl group,1,3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group,1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group,2-chloroethyl group, 2-chloroisobutyl group, 1,2-dichloroethyl group,1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group,1,2,3-trichloropropyl group, bromomethyl group, 1-bromoethyl group,2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group,1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl group,1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group, and 1,2,3-trinitropropyl group.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton has a substituent, and the substituent is a substituted orunsubstituted aryl group or a heteroaryl group.

By introducing an aryl group or a heteroaryl group as the substituent,the Eg(T) can be adjusted and molecular associate can be prevented.Thus, the lifetime can be prolonged.

In the aspect of the invention, the substituent preferably has nocarbazole skeleton.

When a substituent having a carbazole skeleton is introduced, the Eg(T)is largened due to increase in Ip, and thus such a material becomesapplicable as a host for a phosphorescent dopant for emission of ashorter wavelength. However, introduction of a carbazole group, which istypically vulnerable to oxidation, may unfavorably lead to shorterlifetime.

In this respect, since the substituents having carbazole skeleton isexcluded in the above aspect of the invention, though the Eg(T) isreduced, the lifetime can be prolonged.

In the above aspect of the invention, the polycyclic fused aromaticskeleton is preferably selected from the group consisting of asubstituted or unsubstituted phenanthrene-diyl, chrysene-diyl,fluoranthene-diyl and triphenylene-diyl.

Further, the polycyclic fused aromatic skeleton is preferablysubstituted by a group including phenanthrene, chrysene, fluorantheneand triphenylene.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is represented by any one of formulae (1) to (4) as follows.

In the formulae (1) to (4), Ar¹ to Ar⁵ each represent a substituted orunsubstituted fused cyclic structure having 4 to 10 ring-forming carbonatoms (not counting atom(s) of substituent(s)).

Examples of the compounds represented by the above formula (1) aresubstituted or unsubstituted phenanthrene and chrysene.

Examples of the compounds represented by the above formula (2) aresubstituted or unsubstituted acenaphthylene, acenaphthene andfluoranthene.

Examples of the compounds represented by the above formula (3) aresubstituted or unsubstituted benzofluoranthene.

Examples of the compounds represented by the above formula (4) aresubstituted or unsubstituted naphthalene.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is phenanthrene represented by the following formula (50) orits derivative.

Examples of the substituent for the phenanthrene derivative are an alkylgroup, cycloalkyl group, aralkyl group, alkenyl group, cycloalkenylgroup, alkynyl group, hydroxyl group, mercapto group, alkoxy group,alkylthio group, arylether group, arylthioether group, aryl group,heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyanogroup, aldehyde group, carbonyl group, carboxyl group, ester group,amino group, nitro group, silyl group and siloxanyl group.

Examples of the phenanthrene derivative are those represented by thefollowing formula (50A).

In the formula (50A), R₁ to R₁₀ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Examples of the phenanthrene derivative represented by the formula (50)are as follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is chrysene represented by the following formula (51) or itsderivative.

Examples of the chrysene derivative are those represented by thefollowing formula (51A).

In the formula (51A), R₁ to R₁₂ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Examples of the chrysene derivative represented by the formula (51) areas follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is a compound represented by the following formula (52)(benzo[c]phenanthrene) or its derivative.

Examples of the benzo[c]phenanthrene derivative are those represented bythe following formula (52A).

In the formula (52A), R₁ to R₉ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Examples of the benzo[c]phenanthrene derivative represented by theformula (52) are as follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is a compound represented by the following formula (53)(benzo[c]chrysene) or its derivative.

Examples of the benzo[c]chrysene derivative are those represented by thefollowing formula (53A).

In the formula (53A), R₁ to R₁₁ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Examples of the benzo[c]chrysene derivative represented by the formula(53) are as follows.

Preferably In the aspect of the invention, the polycyclic fused aromaticskeleton is a compound represented by the following formula (54)(benzo[c, g]phenanthrene) or its derivative.

Examples of the derivative of such a compound are as follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is fluoranthene represented by the following formula (55) orits derivative.

Examples of the fluoranthene derivative are those represented by thefollowing formula (55A).

In the formula (55A), X₁₂ to X₂₁ each represent a hydrogen atom, ahalogen atom, a linear, branched or cyclic alkyl group, a linear,branched or cyclic alkoxy group, or a substituted or unsubstituted arylgroup.

The aryl group represents a carbocyclic aromatic group such as a phenylgroup and naphthyl group, or a heterocyclic aromatic group such as afuryl group, thienyl group and pyridyl group.

X₁₂ to X₂₁ each preferably represent hydrogen atom, halogen atom (suchas fluorine atom, chlorine atom, or bromine atom), linear, branched orcyclic alkyl group having 1 to 16 carbon atoms (such as methyl group,ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutylgroup, sec-butyl group, tert-butyl group, n-pentyl group, isopentylgroup, neopentyl group, tert-pentyl group, cyclopentyl group, n-hexylgroup, 3,3-dimethylbutyl group, cyclohexyl group, n-heptyl group,cyclohexylmethyl group, n-octyl group, tert-octyl group, 2-ethylhexylgroup, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecylgroup, or n-hexadecyl group), linear, branched or cyclic alkoxy grouphaving 1 to 16 carbon atoms (such as methoxy group, ethoxy group,n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group,sec-butoxy group, n-pentyloxy group, neopentyloxy group, cyclopentyloxygroup, n-hexyloxy group, 3,3-dimethylbutyloxy group, cyclohexyloxygroup, n-heptyloxy group, n-octyloxy group, 2-ethylhexyloxy group,n-nonyloxy group, n-decyloxy group, n-dodecyloxy group, n-tetradecyloxygroup, or n-hexadecyloxy group), or substituted or unsubstituted arylgroup having 4 to 16 carbon atoms (such as phenyl group, 2-methylphenylgroup, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group,4-n-propylphenyl group, 4-isopropylphenyl group, 4-n-butylphenyl group,4-tert-butylphenyl group, 4-isopentylphenyl group, 4-tert-pentylphenylgroup, 4-n-hexylphenyl group, 4-cyclohexylphenyl group, 4-n-octylphenylgroup, 4-n-decylphenyl group, 2,3-dimethylphenyl group,2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 3,4-dimethylphenylgroup, 5-indanyl group, 1,2,3,4-tetrahydro-5-naphthyl group,1,2,3,4-tetrahydro-6-naphthyl group, 2-methoxyphenyl group,3-methoxyphenyl group, 4-methoxyphenyl group, 3-ethoxyphenyl group,4-ethoxyphenyl group, 4-n-propoxyphenyl group, 4-isopropoxyphenyl group,4-n-butoxyphenyl group, 4-n-pentyloxyphenyl group, 4-n-hexyloxyphenylgroup, 4-cyclohexyloxyphenyl group, 4-n-heptyloxyphenyl group,4-n-octyloxyphenyl group, 4-n-decyloxyphenyl group, 2,3-dimethoxyphenylgroup, 2,5-dimethoxyphenyl group, 3,4-dimethoxyphenyl group,2-methoxy-5-methylphenyl group, 3-methyl-4-methoxyphenyl group,2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group,2-chlorophenyl group, 3-chlorophenyl group, 4-chlorophenyl group,4-bromophenyl group, 4-trifluoromethylphenyl group, 3,4-dichlorophenylgroup, 2-methyl-4-chlorophenyl group, 2-chloro-4-methylphenyl group,3-chloro-4-methylphenyl group, 2-chloro-4-methoxyphenyl group,4-phenylphenyl group, 3-phenylphenyl group, 4-(4′-methylphenyl)phenylgroup, 4-(4′-methoxyphenyl)phenyl group, 1-naphthyl group, 2-naphthylgroup, 4-ethoxy-1-naphthyl group, 6-methoxy-2-naphthyl group,7-ethoxy-2-naphthyl group, 2-furyl group, 2-thienyl group, 3-thienylgroup, 2-pyridyl group, 3-pyridyl group, or 4-pyridyl group), morepreferably hydrogen atom, fluorine atom, chlorine atom, alkyl grouphaving 1 to 10 carbon atoms, alkoxy group having 1 to 10 carbon atoms oraryl group having 6 to 12 carbon atoms, further more preferably hydrogenatom, fluorine atom, chlorine atom, alkyl group having 1 to 6 carbonatoms, alkoxy group having 1 to 6 carbon atoms or carbocyclic aromaticgroup having 6 to 10 carbon atoms.

Examples of the fluoranthene derivative represented by the formula (55)are as follows.

Examples of the substituted or unsubstituted benzofluoranthene arebenzo[b]fluoranthene represented by the following formula (551) or itsderivative and benzo[k]fluoranthene represented by a formula (552) orits derivative.

In the formulae (551) and (552), X¹ to X²⁴ each represent a hydrogenatom, a halogen atom, a linear, branched or cyclic alkyl group, alinear, branched or cyclic alkoxy group, or a substituted orunsubstituted aryl group.

The aryl group represents a carbocyclic aromatic group such as a phenylgroup and naphthyl group, or a heterocyclic aromatic group such as afuryl group, thienyl group and pyridyl group.

X¹ to X²⁴ each preferably represent hydrogen atom, halogen atom (such asfluorine atom, chlorine atom, or bromine atom), linear, branched orcyclic alkyl group having 1 to 16 carbon atoms (such as methyl group,ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutylgroup, sec-butyl group, tert-butyl group, n-pentyl group, isopentylgroup, neopentyl group, tert-pentyl group, cyclopentyl group, n-hexylgroup, 3,3-dimethylbutyl group, cyclohexyl group, n-heptyl group,cyclohexylmethyl group, n-octyl group, tert-octyl group, 2-ethylhexylgroup, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecylgroup, or n-hexadecyl group), linear, branched or cyclic alkoxy grouphaving 1 to 16 carbon atoms (such as methoxy group, ethoxy group,n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group,sec-butoxy group, n-pentyloxy group, neopentyloxy group, cyclopentyloxygroup, n-hexyloxy group, 3,3-dimethylbutyloxy group, cyclohexyloxygroup, n-heptyloxy group, n-octyloxy group, 2-ethylhexyloxy group,n-nonyloxy group, n-decyloxy group, n-dodecyloxy group, n-tetradecyloxygroup, or n-hexadecyloxy group), or substituted or unsubstituted arylgroup having 4 to 16 carbon atoms (such as phenyl group, 2-methylphenylgroup, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group,4-n-propylphenyl group, 4-isopropylphenyl group, 4-n-butylphenyl group,4-tert-butylphenyl group, 4-isopentylphenyl group, 4-tert-pentylphenylgroup, 4-n-hexylphenyl group, 4-cyclohexylphenyl group, 4-n-octylphenylgroup, 4-n-decylphenyl group, 2,3-dimethylphenyl group,2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 3,4-dimethylphenylgroup, 5-indanyl group, 1,2,3,4-tetrahydro-5-naphthyl group,1,2,3,4-tetrahydro-6-naphthyl group, 2-methoxyphenyl group,3-methoxyphenyl group, 4-methoxyphenyl group, 3-ethoxyphenyl group,4-ethoxyphenyl group, 4-n-propoxyphenyl group, 4-isopropoxyphenyl group,4-n-butoxyphenyl group, 4-n-pentyloxyphenyl group, 4-n-hexyloxyphenylgroup, 4-cyclohexyloxyphenyl group, 4-n-heptyloxyphenyl group,4-n-octyloxyphenyl group, 4-n-decyloxyphenyl group, 2,3-dimethoxyphenylgroup, 2,5-dimethoxyphenyl group, 3,4-dimethoxyphenyl group,2-methoxy-5-methylphenyl group, 3-methyl-4-methoxyphenyl group,2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group,2-chlorophenyl group, 3-chlorophenyl group, 4-chlorophenyl group,4-bromophenyl group, 4-trifluoromethylphenyl group, 3,4-dichlorophenylgroup, 2-methyl-4-chlorophenyl group, 2-chloro-4-methylphenyl group,3-chloro-4-methylphenyl group, 2-chloro-4-methoxyphenyl group,4-phenylphenyl group, 3-phenylphenyl group, 4-(4′-methylphenyl)phenylgroup, 4-(4′-methoxyphenyl)phenyl group, 1-naphthyl group, 2-naphthylgroup, 4-ethoxy-1-naphthyl group, 6-methoxy-2-naphthyl group,7-ethoxy-2-naphthyl group, 2-furyl group, 2-thienyl group, 3-thienylgroup, 2-pyridyl group, 3-pyridyl group, or 4-pyridyl group), morepreferably hydrogen atom, fluorine atom, chlorine atom, alkyl grouphaving 1 to 10 carbon atoms, alkoxy group having 1 to 10 carbon atoms oraryl group having 6 to 12 carbon atoms, further more preferably hydrogenatom, fluorine atom, chlorine atom, alkyl group having 1 to 6 carbonatoms, alkoxy group having 1 to 6 carbon atoms or carbocyclic aromaticgroup having 6 to 10 carbon atoms.

Examples of the benzo[b]fluoranthene derivative represented by theformula (551) are as follows.

Examples of the benzo[k]fluoranthene derivative represented by theformula (552) are as follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is triphenylene represented by the following formula (56) orits derivative.

Examples of the triphenylene derivative are those represented by thefollowing formula (56A).

In the formula (56A), R₁ to R₆ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Examples of the triphenylene derivative represented by the formula (56)are as follows.

Preferably in the aspect of the invention, the polycyclic fused aromaticskeleton is naphthalene or its derivative.

Examples of the naphthalene derivative are those represented by thefollowing formula (57A).

In the formula (57A), R₁ to R₈ respectively independently represent: ahydrogen atom; a substituent including substituted or unsubstituted arylgroup having 5 to 30 ring-forming carbon atoms (not counting carbonatom(s) of substituent(s)), branched or linear alkyl group having 1 to30 carbon atoms or substituted or unsubstituted cycloalkyl group having3 to 20 carbon atoms; or a combination of the substituents.

Specific examples of the naphthalene derivative are those represented bythe following formulae.

The polycyclic fused aromatic skeleton may contain a nitrogen atom,examples of which are shown below.

Further, for instance, the fluorene compounds shown below are usable asthe host of the invention.

In the above aspect of the invention, the first host is preferably asubstituted or unsubstituted phenanthrene, chrysene, triphenylene,naphthalene or fluoranthene.

Examples of the phenanthrene, chrysene, triphenylene, naphthalene andfluoranthene are those represented above.

When the first host is provided by the substituted or unsubstitutedphenanthrene, chrysene, triphenylene, naphthalene or fluoranthene, sincethe first host is provided by a polycyclic fused aromatic compound andexhibits the Eg(T) in a range from 2.1 to 2.7 eV, efficiency andlifetime of a red or green-emitting phosphorescent organicelectroluminescence device can be enhanced.

In the above aspect of the invention, the first host is preferably asubstituted or unsubstituted phenanthrene or chrysene.

In the above aspect of the invention, the second host preferablyincludes the substituted or unsubstituted polycyclic fused aromaticskeleton having 10 to 30 ring-forming atoms (not counting atom(s) ofsubstituent(s)).

In the above aspect of the invention, the second host is preferably asubstituted or unsubstituted phenanthrene or chrysene.

Examples of the phenanthrene or chrysene are those represented above.

In the above aspect of the invention, the first host preferably has thepolycyclic fused aromatic skeleton, an affinity level of the second hostis preferably higher than the affinity level of the first host, and acontent of the second host in the host is preferably in a range from 1mass % to 50 mass %.

When the content of the second host is less than 1 mass % of the entirehost, the production of the device becomes unfavorably difficult. On theother hand, when the content of the second host exceed 50 mass % of theentire host, the shortage of the content of the first host may result indeterioration in luminous efficiency and decrease in emission lifetime.

Incidentally, the content of the second host in the entire host is morepreferably in a range from 5 mass % to 49 mass %.

Preferably in the aspect of the invention, the phosphorescent dopantcontains a metal complex having: a metal selected from Ir, Pt, Os, Au,Cu, Re and Ru; and a ligand.

Examples of the dopants are PQIr (iridium(III)bis(2-phenylquinolyl-N,C^(2′)) acetylacetonate) and Ir(ppy)₃(fac-tris(2-phenylpyridine)iridium). Further examples are compoundsshown below.

In the above aspect of the invention, a wavelength of a light of amaximum luminance of the phosphorescent dopant is preferably in a rangefrom 500 nm to 700 nm.

The wavelength at the maximum luminance is preferably in a range from580 nm to 680 nm, further preferably in a range from 600 nm to 660 nm.

By doping the phosphorescent dopant having such an emission wavelengthto the host material usable for the invention so as to form the emittinglayer, an organic electroluminescence device with a high efficiency canbe provided.

In the above aspect of the invention, the organic thin-film layercomprises an electron injecting layer between the cathode and thephosphorescent-emitting layer, and the electron injecting layerpreferably contains a nitrogen-containing heterocyclic derivative.

The electron injecting layer or the electron transporting layer, whichaids injection of the electrons into the emitting layer, has a highelectron mobility. The electron injecting layer is provided foradjusting energy level, by which, for instance, sudden changes in theenergy level can be reduced. As a material for the electron injectinglayer or the electron transporting layer, 8-hydroxyquinoline or a metalcomplex of its derivative, an oxadiazole derivative and anitrogen-containing heterocyclic derivative are preferable. An exampleof the 8-hydroxyquinoline or the metal complex of its derivative is ametal chelate oxinoid compound containing a chelate of oxine (typically8-quinolinol or 8-hydroxyquinoline). For instance, tris(8-quinolinol)aluminum can be used. Examples of the oxadiazole derivative are asfollows.

In the formula, Ar¹⁷, Ar¹⁸, Ar¹⁹, Ar²¹, Ar²² and Ar²⁵ each represent asubstituted or unsubstituted aryl group. Ar¹⁷, Ar¹⁹ and Ar²² may be thesame as or different from Ar¹⁸, Ar²¹ and Ar²⁵ respectively. Ar²⁰, Ar²³and Ar²⁴ each represent a substituted or unsubstituted arylene group.Ar²³ and Ar²⁴ may be mutually the same or different.

Examples of the arylene group are a phenylene group, naphthylene group,biphenylene group, anthranylene group, perylenylene group and pyrenylenegroup. Examples of the substituent therefor are an alkyl group having 1to 10 carbon atoms, alkoxy group having 1 to 10 carbon atoms and cyanogroup. Such an electron transport compound is preferably an electrontransport compound that can be favorably formed into a thin film(s).Examples of the electron transport compounds are as follows.

An example of the nitrogen-containing heterocyclic derivative is anitrogen-containing compound that is not a metal complex, the derivativebeing formed of an organic compound represented by one of the followinggeneral formulae. Examples of the nitrogen-containing heterocyclicderivative are five-membered ring or six-membered ring derivative havinga skeleton represented by the formula (A) and a derivative having astructure represented by the formula (B).

In the formula (B), X represents a carbon atom or nitrogen atom. Z₁ andZ₂ each independently represent an atom group capable of forming anitrogen-containing heterocycle.

Preferably, the nitrogen-containing heterocyclic derivative is anorganic compound having a nitrogen-containing aromatic polycyclic grouphaving a five-membered ring or six-membered ring. When thenitrogen-containing heterocyclic derivative includes suchnitrogen-containing aromatic polycyclic series having plural nitrogenatoms, the nitrogen-containing heterocyclic derivative may be anitrogen-containing aromatic polycyclic organic compound having askeleton formed by a combination of the skeletons respectivelyrepresented by the formulae (A) and (B), or by a combination of theskeletons respectively represented by the formulae (A) and (C).

A nitrogen-containing group of the nitrogen-containing organic compoundis selected from nitrogen-containing heterocyclic groups respectivelyrepresented by the following general formulae.

In the respective formulae: R represents an aryl group having 6 to 40carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, an alkylgroup having 1 to 20 carbon atoms or an alkoxy group having 1 to 20carbon atoms; and n represents an integer in a range of 0 to 5. When nis an integer of 2 or more, the plurality of R may be mutually the sameor different.

A preferable specific compound is a nitrogen-containing heterocyclicderivative represented by the following formula.HAr-L¹-Ar¹-Ar²  [Chemical Formula 62]In the formula, HAr represents a substituted or unsubstitutednitrogen-containing heterocycle having 3 to 40 carbon atoms; L¹represents a single bond, a substituted or unsubstituted arylene grouphaving 6 to 40 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 3 to 40 carbon atoms; Ar¹ represents asubstituted or unsubstituted divalent aromatic hydrocarbon group having6 to 40 carbon atoms; and Ar² represents a substituted or unsubstitutedaryl group having 6 to 40 carbon atoms, or a substituted orunsubstituted heteroaryl group having 3 to 40 carbon atoms.

HAr is exemplarily selected from the following group.

L¹ is exemplarily selected from the following groups.

Ar² is exemplarily selected from the following groups.

Ar¹ is exemplarily selected from the following arylanthranil groups.

In the formula, R¹ to R¹⁴ each independently represent a hydrogen atom,halogen atom, alkyl group having 1 to 20 carbon atoms, alkoxy grouphaving 1 to 20 carbon atoms, aryloxy group having 6 to 40 carbon atoms,substituted or unsubstituted aryl group having 6 to 40 carbon atoms orheteroaryl group having 3 to 40 carbon atoms. Ar³ represents asubstituted or unsubstituted aryl group having 6 to 40 carbon atoms orheteroaryl group having 3 to 40 carbon atoms.

The nitrogen-containing heterocyclic derivative is also preferably anitrogen-containing heterocyclic derivative in which R¹ to R⁸ in thestructure of Ar¹ represented by the above formula each represent ahydrogen atom.

Other than the above, the following compound (see JP-A-9-3448) can befavorably used.

In the formula, R₁ to R₄ each independently represent a hydrogen atom, asubstituted or unsubstituted aliphatic group, a substituted orunsubstituted alicyclic group, a substituted or unsubstitutedcarbocyclic aromatic ring group, or substituted or unsubstitutedheterocyclic group. X₁ and X₂ each independently represent an oxygenatom, a sulfur atom or a dicyanomethylene group.)

Alternatively, the following compound (see JP-A-2000-173774) can also befavorably used.

In the formula, R¹, R², R³ and R⁴, which may be mutually the same ordifferent, each represent an aryl group represented by the followingformula.

In the formula, R⁵, R⁶, R⁷, R⁸ and R⁹, which may be mutually the same ordifferent, each represent a hydrogen atom, a saturated or unsaturatedalkoxyl group, an alkyl group, an amino group or an alkylamino group. Atleast one of R⁵, R⁶, R⁷, R⁸ and R⁹ represents a saturated or unsaturatedalkoxyl group, an alkyl group, an amino group or an alkylamino group.

A polymer compound containing the nitrogen-containing heterocyclic groupor a nitrogen-containing heterocyclic derivative may be used.

The electron transporting layer preferably contains at least one ofnitrogen-containing heterocycle derivatives respectively represented bythe following formulae (201) to (203).

In the formulae (201) to (203), R represents a hydrogen atom, asubstituted or unsubstituted aryl group having 6 to 60 carbon atoms, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted quinolyl group, a substituted or unsubstituted alkyl grouphaving 1 to 20 carbon atoms, or a substituted or unsubstituted alkoxygroup having 1 to 20 carbon atoms. n represents an integer of 0 to 4.

R¹ represents a substituted or unsubstituted aryl group having 6 to 60carbon atoms, a substituted or unsubstituted pyridyl group, asubstituted or unsubstituted quinolyl group, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, or an alkoxygroup having 1 to 20 carbon atoms.

R² and R³ respectively independently represent a substituted orunsubstituted aryl group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridyl group, a substituted or unsubstituted quinolylgroup, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 20carbon atoms.

L represents a substituted or unsubstituted arylene group having 6 to 60carbon atoms, a substituted or unsubstituted pyridinylene group, asubstituted or unsubstituted quinolinylene group, or a substituted orunsubstituted fluorenylene group.

Ar¹ represents a substituted or unsubstituted arylene group having 6 to60 carbon atoms, a substituted or unsubstituted pyridinylene group, or asubstituted or unsubstituted quinolinylene group.

Ar² represents a substituted or unsubstituted aryl group having 6 to 60carbon atoms, a substituted or unsubstituted pyridyl group, asubstituted or unsubstituted quinolyl group, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, or a substitutedor unsubstituted alkoxy group having 1 to 20 carbon atoms.

Ar³ represents a substituted or unsubstituted aryl group having 6 to 60carbon atoms, a substituted or unsubstituted pyridyl group, asubstituted or unsubstituted quinolyl group, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 20 carbon atoms, or a grouprepresented by -Ar¹-Ar² (Ar¹ and Ar² may be the same as the above(-Ar³=-Ar¹-Ar²)).

Examples of the substituents of -Ar¹, -Ar² and -Ar³ are a substituted orunsubstituted aryl group, a pyridyl group, a quinolyl group and an alkylgroup having 6 to 20 carbon atoms.

When L and Ar¹ are not symmetrical, either of the substitution sites ofAr¹ and Ar² jointed to L and Ar¹ may be selected.

In the formulae (201) to (203), R represents a hydrogen atom, asubstituted or unsubstituted aryl group having 6 to 60 carbon atoms, asubstituted or unsubstituted pyridyl group, substituted or unsubstitutedquinolyl group, a substituted or unsubstituted alkyl group having 1 to20 carbon atoms, or a substituted or unsubstituted alkoxy group having 1to 20 carbon atoms.

The aryl group having 6 to 60 carbon atom is preferably an aryl grouphaving 6 to 40 carbon atoms, more preferably an aryl group having 6 to20 carbon atoms. Examples of such an aryl group are a phenyl group,naphthyl group, anthryl group, phenanthryl group, naphthacenyl group,chrysenyl group, pyrenyl group, biphenyl group, terphenyl group, tolylgroup, t-butylphenyl group, (2-phenylpropyl)phenyl group, fluoranthenylgroup, fluorenyl group, a monovalent group formed of spirobifluorene,perfluorophenyl group, perfluoronaphthyl group, perfluoroanthryl group,perfluorobiphenyl group, a monovalent group formed of9-phenylanthracene, a monovalent group formed of 9-(1′naphthyl)anthracene, a monovalent group formed of 9-(2′-naphthyl)anthracene, amonovalent group formed of 6-phenylchrysene, and a monovalent groupformed of 9-[4-(diphenylamine)phenyl]anthracene, among which a phenylgroup, naphthyl group, biphenyl group, terphenyl group,9-(10-phenyl)anthryl group, 9-[10-(1′-naphthyl)]anthryl group and9-[10-(2′-naphthyl)]anthryl group are preferable.

The alkyl group having 1 to 20 carbon atoms is preferably an alkyl grouphaving 1 to 6 carbon atoms. Examples of such an alkyl group are a methylgroup, ethyl group, propyl group, butyl group, pentyl group, hexylgroup, and a haloalkyl group such as trifluoromethyl group. When such analkyl group has 3 or more carbon atoms, the alkyl group may be linear,cyclic or branched.

The alkoxy group having 1 to 20 carbon atoms is preferably an alkoxygroup having 1 to 6 carbon atoms. Examples of such an alkoxy group are amethoxy group, ethoxy group, propoxy group, butoxy group, pentyloxygroup, and hexyloxy group. When such an alkoxy group has 3 or morecarbon atoms, the alkoxy group may be linear, cyclic or branched.

Examples of a substituent for the group represented by R are a halogenatom, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbonatoms, a substituted or unsubstituted aryloxy group having 6 to 40carbon atoms, a substituted or unsubstituted aryl group having 6 to 40carbon atoms, or a substituted or unsubstituted heteroaryl group having3 to 40 carbon atoms.

Examples of the halogen atom are fluorine, chlorine, bromine, iodine andthe like.

Examples for each of the alkyl group having 1 to 20 carbon atoms, thealkoxy group having 1 to 20 carbon atoms, and an aryl group having 6 to40 carbon atoms may be the same as the above examples.

Examples of the aryloxy group having 6 to 40 carbon atoms are a phenoxygroup and a biphenyloxy group.

Examples of the heteroaryl group having 3 to 40 carbon atoms are apyroryl group, furyl group, thienyl group, silolyl group, pyridyl group,quinolyl group, isoquinolyl group, benzofuryl group, imidazolyl group,pyrimidyl group, carbazolyl group, selenophenyl group, oxadiazolyl groupand triazolyl group.

n is an integer in a range of 0 to 4, preferably 0 to 2.

In the formulae (201), R¹ represents a substituted or unsubstituted arylgroup having 6 to 60 carbon atoms, a substituted or unsubstitutedpyridyl group, a substituted or unsubstituted quinolyl group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, oran alkoxy group having 1 to 20 carbon atoms.

Examples for each of the groups, the preferable number of carbon atomscontained in each of the groups, and preferable examples of thesubstituent for each of the groups are the same as those described inrelation to R.

In the formulae (202) and (203), R² and R³ each independently representa hydrogen atom, a substituted or unsubstituted aryl group having 6 to60 carbon atoms, a substituted or unsubstituted pyridyl group,substituted or unsubstituted quinolyl group, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, or a substitutedor unsubstituted alkoxy group having 1 to 20 carbon atoms.

Examples for each of the groups, the preferable number of carbon atomscontained in each of the groups, and preferable examples of thesubstituent for each of the groups are the same as those described inrelation to R.

In the formulae (201) to (203), L represents a substituted orunsubstituted arylene group having 6 to 60 carbon atoms, a substitutedor unsubstituted pyridinylene group, a substituted or unsubstitutedquinolinylene group, or a substituted or unsubstituted fluorenylenegroup.

The arylene group having 6 to 60 carbon atoms is preferably an arylenegroup having 6 to 40 carbon atoms, more preferably an arylene grouphaving 6 to 20 carbon atoms. An example of such an arylene group is adivalent group formed by removing one hydrogen atom from the aryl grouphaving been described in relation to R. Examples of a substituent forthe group represented by L are the same as those described in relationto R.

Further, L may preferably be a group selected from groups represented bythe following formulae.

In the formula (201), Ar¹ represents a substituted or unsubstitutedarylene group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridinylene group, or a substituted or unsubstitutedquinolinylene group. Examples of a substituent for the group representedby Ar¹ and Ar³ are the same as those described in relation to R.

Alternatively, Ar¹ is preferably selected from a group consisting offused ring groups respectively represented by the following formulae(101) to (110).

In the formulae (101) to (110), the fused ring groups each may be linkedwith a link group formed of a halogen atom, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted orunsubstituted aryloxy group having 6 to 40 carbon atoms, a substitutedor unsubstituted aryl group having 6 to 40 carbon atoms or a substitutedor unsubstituted heteroaryl group having 3 to 40 carbon atoms. When therings each are linked with plural link groups, the plural link groupsmay be mutually the same or different. Examples for each of the groupsare the same as those described above.

In the formula (110), L′ represents a group selected from the groupsrepresented by the following formulae.

The structure of Ar¹ represented by the formula (103) is preferably afused ring group represented by any one of the following formulae (111)to (125).

In the formulae (111) to (125), the fused rings each may be linked witha link group formed of a halogen atom, a substituted or unsubstitutedalkyl group having 1 to 20 carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 20 carbon atoms, a substituted or unsubstitutedaryloxy group having 6 to 40 carbon atoms, a substituted orunsubstituted aryl group having 6 to 40 carbon atoms or a substituted orunsubstituted heteroaryl group having 3 to 40 carbon atoms. When therings each are linked with plural link groups, the plural link groupsmay be mutually the same or different. Examples for each of the groupsare the same as those described above.

In the formula (201), Ar² represents a substituted or unsubstituted arylgroup having 6 to 60 carbon atoms, a substituted or unsubstitutedpyridyl group, substituted or unsubstituted quinolyl group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, ora substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms.

Examples for each of the groups, the preferable number of carbon atomscontained in each of the groups, and preferable examples of thesubstituent for each of the groups are the same as those described inrelation to R.

In the above formulae (202) and (203), Ar³ represents a substituted orunsubstituted aryl group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridyl group, a substituted or unsubstituted quinolylgroup, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbonatoms, or a group represented by -Ar¹-Ar² (Ar¹ and Ar² may be the sameas the above).

Examples for each of the groups, the preferable number of carbon atomscontained in each of the groups, and preferable examples of thesubstituent for each of the groups are the same as those described inrelation to R.

Alternatively, Ar³ is preferably selected from a group consisting offused ring groups respectively represented by the following formulae(126) to (135).

In the formulae (126) to (135), the fused ring groups each may be linkedwith a link group formed of a halogen atom, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted orunsubstituted aryloxy group having 6 to 40 carbon atoms, a substitutedor unsubstituted aryl group having 6 to 40 carbon atoms or a substitutedor unsubstituted heteroaryl group having 3 to 40 carbon atoms. When therings each are linked with plural link groups, the plural link groupsmay be mutually the same or different. Examples for each of the groupsare the same as those described above.

In the formula (135), L′ represents the same as the above.

In the formulae (126) to (135), R′ represents a hydrogen atom, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, asubstituted or unsubstituted aryl group having 6 to 40 carbon atoms, ora substituted or unsubstituted heteroaryl group having 3 to 40 carbonatoms. Examples for each of the groups are the same as those describedabove.

The structure of Ar³ represented by the formula (128) is preferably afused ring group represented by any one of the following formulae (136)to (158).

In the formulae (136) to (158), the fused ring groups each may be linkedwith a link group formed of a halogen atom, a substituted orunsubstituted alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted orunsubstituted aryloxy group having 6 to 40 carbon atoms, a substitutedor unsubstituted aryl group having 6 to 40 carbon atoms or a substitutedor unsubstituted heteroaryl group having 3 to 40 carbon atoms. When therings each are linked with plural link groups, the plural link groupsmay be mutually the same or different. Examples for each of the groupsare the same as those described above. R′ is the same as the above.

Preferably, Ar² and Ar³ may respectively independently be a groupselected from the groups represented by the following formulae.

Examples of the nitrogen-containing heterocyclic derivative representedby any one of the general formulae (201) to (203) according to thepresent invention will be shown below. However, the present invention isnot limited to the exemplary compounds shown below.

In the chart shown below, HAr represents any one of structuresrepresented by the formulae (201) to (203).

In the following exemplary compounds, the exemplary compounds 1-1 to1-17, 2-1 to 2-9, 3-1 to 3-6, 4-1 to 4-12, 5-1 to 5-6, 6-1 to 6-5 and8-1 to 8-13 correspond to the formula (201). The exemplary compounds 9-1to 9-17, 10-1 to 10-9, 11-1 to 11-6, 12-1 to 12-11, 13-1 to 13-6 and14-1 to 14-5 correspond to the formula (202). The exemplary compounds7-1 to 7-10, 15-1 to 15-13, 16-1 to 16-8 and 17-1 to 17-8 correspond tothe formula (203).

[Chemical Formula 79] HAr—L—Ar¹—Ar² HAr L Ar¹ Ar² 1-1 

 2

 3

 4

 5

 6

 7

 8

 9

10

11

12

13

14

[Chemical Formula 80] HAr—L—Ar¹—Ar² HAr L Ar¹ Ar² 1-15

—   16

—   17

—

[Chemical Formula 81] HAr L Ar¹ Ar² HAr L Ar¹ Ar² 2-1  

2

3

4

5

6

7

8

9

[Chemical Formula 82] HAr L Ar¹ Ar² HAr L Ar¹ Ar² 3-1  

2

3

4

5

6

[Chemical Formula 83] HAr L Ar¹ Ar² HAr L Ar¹ Ar² 4-1  

2

3

4

5

6

7

8

9

10 

11 

12 

[Chemical Formula 84] HAr—L—Ar¹—Ar² HAr L Ar¹ Ar² 5-1

2

3

4

5

6

[Chemical Formula 85] HAr—L—Ar¹—Ar² HAr L Ar¹ Ar² 6-1

2

3

4

5

[Chemical Formula 86] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 7-1

2

3

4

5

6

7

8

9

10

[Chemical Formula 87] HAr—L—Ar¹—Ar² HAr L Ar¹ Ar² 8-1

2

3

4

5

6

7

8

9

10

11

12

13

[Chemical Formula 88] HAr—L—Ar³(Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 9-1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

12

13

14

[Chemical Formula 89] HAr—L—Ar³(—Ar³═—Ar^(l)—Ar²) HAr L Ar¹ Ar² 9-15

— 16

— 17

—

[Chemical Formula 90] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 10-1

2

3

4

5

6

7

8

9

[Chemical Formula 91] HAr—L—Ar³(Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 11-1

2

3

4

5

6

[Chemical Formula 92] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 12-1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

[Chemical Formula 93] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 13-1

2

3

4

5

6

[Chemical Formula 94] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 14-1

2

3

4

5

[Chemical Formula 95] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 15-1

2

3

4

5

6

7

8

9

10

[Chemical Formula 96] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 15-11

— 12

— 13

—

[Chemical Formula 97] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 16-1

2

3

4

5

6

7

8

[Chemical Formula 98] HAr—L—Ar³(—Ar³═—Ar¹—Ar²) HAr L Ar¹ Ar² 17-1

2

3

4

5

6

7

8

Among the above examples, examples (1-1), (1-5), (1-7), (2-1), (3-1),(4-2), (4-6), (7-2), (7-7), (7-8), (7-9) and (9-7) are particularlypreferred.

Although thickness of the electron injecting layer or the electrontransporting layer is not specifically limited, the thickness ispreferably 1 to 100 nm.

In the aspect of the invention, a reduction-causing dopant is present atan interfacial region between the cathode and the organic thin-filmlayer.

With this arrangement, the organic electroluminescence device can emitlight with enhanced luminance intensity and have a longer lifetime.

Here, a reduction-causing dopant is defined as a material that canreduce an electron transport compound. Thus, various substances having acertain level of reducibility can be used, preferable examples of whichare at least one substance selected from a group consisting of: alkalimetal, alkali earth metal, rare earth metal, an oxide of the alkalimetal, a halogenide of the alkali metal, an oxide of the alkali earthmetal, a halogenide of the alkali earth metal, an oxide of the rareearth metal, a halogenide of the rare earth metal, an organic complex ofthe alkali metal, an organic complex of the alkali earth metal and anorganic complex of the rare earth metal.

Specifically, a preferable reduction-causing dopant is at least onealkali metal selected from a group consisting of Li (work function: 2.9eV), Na (work function: 2.36 eV), K (work function: 2.28 eV), Rb (workfunction: 2.16 eV) and Cs (work function: 1.95 eV), or at least onealkali earth metal selected from a group consisting of Ca (workfunction: 2.9 eV), Sr (work function: 2.0 to 2.5 eV) and Ba (workfunction: 2.52 eV). A substance having work function of 2.9 eV or lessis particularly preferable.

Among the above, a more preferable reduction-causing dopant is at leastone alkali metal selected from a group consisting of K, Rb and Cs. Afurther more preferable reduction-causing dopant is Rb or Cs. The mostpreferable reduction-causing dopant is Cs. Since the above alkali metalshave particularly high reducibility, addition of a relatively smallamount of these alkali metals to an electron injecting zone can enhanceluminance intensity and lifetime of the organic electroluminescencedevice. As a reduction-causing dopant having work function of 2.9 eV orless, a combination of two or more of the alkali metals is alsopreferable. Particularly, a combination including Cs (e.g., Cs and Na,Cs and K, Cs and Rb, or Cs, Na and K) is preferable. A reduction-causingdopant containing Cs in a combining manner can efficiently exhibitreducibility. Addition of the reduction-causing dopant to the electroninjecting zone can enhance luminance intensity and lifetime of theorganic electroluminescence device.

An organic-electroluminescent-material-containing solution according toanother aspect of the invention is for preparing aphosphorescent-emitting layer of the organic electroluminescence deviceaccording to the above aspect of the invention, the solution including:the host; the phosphorescent dopant; and a solvent in which the host andthe phosphorescent dopant are dissolved.

According to the organic-electroluminescent-material-containingsolution, the above phosphorescent-emitting layer can be easily andinexpensively formed with the use of ink-printing method, nozzle-jetmethod and the like.

Examples of the solvent of theorganic-electroluminescent-material-containing solution are biphenylderivative and cyclic ketone.

An example of the biphenyl derivative is an alkyl-substituted biphenyl.Specific examples of the alkyl-substituted biphenyl are methyl biphenyl,ethyl biphenyl, diethyl biphenyl, isopropyl biphenyl, diisopropylbiphenyl, n-propyl biphenyl, n-penthyl biphenyl and methoxy biphenyl.

Incidentally, the carbon number of the alkyl group of thealkyl-substituted biphenyl is preferably in a range from 1 to 5. Withthe above range, both appropriate viscosity and appropriate solubilitycan be exhibited.

For instance, ethyl biphenyl, isopropyl biphenyl and the like can besuitably used as the solvent of theorganic-electroluminescent-material-containing solution.

Incidentally, the solvent may be provided solely by the biphenylderivative, or, alternatively, the solvent may be provided by a solutionof the biphenyl derivative mixed with viscosity control reagent and thelike.

When the solvent is provided by a mixed solution, the mixed solution maycontain 20% or more of the biphenyl derivative or, alternatively, 50% ormore of the biphenyl derivative or, further alternatively, 75% or moreof the biphenyl derivative. In order to utilize the viscosity andsolubility of the biphenyl derivative, the percentage of the biphenylderivative is preferably high.

Examples of cyclic ketone include cyclic alkyl ketones such ascyclopentanone derivative, cyclohexanone derivative, cycloheptanonederivative and cyclooctanone derivative. One of the above cyclic ketonesmay be singularly used, or a mixture of plurality thereof may be used.

Particularly, the solvent preferably contains a cyclic ketone in theform of cyclohexanone derivative.

Preferable cyclohexanone derivatives are: 2-acetylcyclohexanone;2-methylcyclohexanone; 3-methylcyclohexanone; 4-methylcyclohexanone;2-cyclohexylcyclohexanone; 2-(1-cyclohexenyl)cyclohexanone;2,5-dimethylcyclohexanone; 3,4-dimethylcyclohexanone;3,5-dimethylcyclohexanone; 4-ethylcyclohexanone; pulegone; menthone;4-pentylcyclohexanone; 2-propylcyclohexanone;3,3,5-trimethylcyclohexanone; and thujone.

Among the above, cyclohexanone is particularly preferable.

Cyclic ketones including a nitrogen-containing ring are also preferable,examples of which are: caprolactam; N-methylcaprolactam;1,3-dimethyl-2-imidazolidine; 2-pyrrolidone; 1-acetyl-2-pyrrolidone;1-buthyl-2-pyrrolidone; 2-piperidone; and 1,5-dimethyl-2-piperidone.

The cyclic ketone compounds are preferably selected from the group ofcyclohexanone, cyclopentanone and cycloheptanone (including derivativesthereof).

After various researches, the inventors have found that cyclohexanonederivatives are capable of dissolving low-molecular organicelectroluminescent material at a concentration higher than the othersolvents and also capable of dissolving not limited range of compounds,thus allowing preparation oforganic-electroluminescent-material-containing solution that utilizesvarious low-molecular organic electroluminescent materials.

Further, it has been found that, with the use of cyclohexanonederivative as the solvent, anorganic-electroluminescent-material-containing solution that containssufficient amount of high-performance low-molecular organicelectroluminescent material that could not be used in a typical solventon account of low solubility thereof can be prepared.

Further, cyclohexanone derivatives are suitable for coating process suchas inkjet method in view of a high boiling point (156 degrees C.:cyclohexanone) and a high viscosity (2 cP: cyclohexanone) thereof.Furthermore, since cyclohexanone derivatives are favorably mixed with analcohol solvent (a viscosity control reagent), especially with a diolsolvent, a highly viscous solution can be prepared by adjusting theviscosity, which is advantageous as a solvent of low-molecular organicelectroluminescent material of which viscosity does not change only bydissolving.

Incidentally, the solvent of theorganic-electroluminescent-material-containing solution of the inventionis not limited to the above biphenyl derivatives and cyclic ketones, butmay alternatively alcohols (e.g. methanol and ethanol), carboxylateesters (e.g. ethyl acetate and propyl acetate), nitriles (e.g.acetonitrile), ethers (e.g. isopropyl ether and THF), aromatichydrocarbons (e.g. cyclohexyl benzene, toluene and xylene), alkylhalides (e.g. methylene chloride) and saturated hydrocarbons (e.g.heptane).

Among the above, carboxylate esters, nitriles, ethers, aromatichydrocarbons, alkyl halides and saturated hydrocarbons are preferable.Carboxylate esters, ethers and aromatic hydrocarbons are morepreferable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an outline structure of an organic electroluminescencedevice according to an exemplary embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferable exemplary embodiment(s) of the invention will be describedbelow.

Organic Electroluminescence Device

FIG. 1 shows a schematic arrangement of an organic electroluminescencedevice according to an exemplary embodiment of, the invention.

An organic electroluminescence device 1 includes a transparent substrate2, an anode 3, a cathode 4 and an organic thin-film layer 10 disposedbetween the anode 3 and the cathode 4.

The organic thin-film layer 10 includes a phosphorescent-emitting layer5 containing a phosphorescent host and a phosphorescent dopant. A layersuch as a hole injecting/transporting layer (i.e. at least one ofhole-injecting layer and hole-transporting layer) 6 may be providedbetween the phosphorescent-emitting layer 5 and the anode 3 while alayer such as an electron injecting/transporting layer (i.e. at leastone of electron-injecting layer and electron-transporting layer) 7 maybe provided between the phosphorescent-emitting layer 5 and the cathode4.

In addition, an electron blocking layer may be provided to thephosphorescent-emitting layer 5 adjacent to the anode 3 while a holeblocking layer may be provided to the phosphorescent-emitting layer 5adjacent to the cathode 4.

With this arrangement, electrons and holes can be trapped in thephosphorescent-emitting layer 5, thereby enhancing probability ofexciton generation in the phosphorescent-emitting layer 5.

EXAMPLES

Next, the invention will be described in further detail by exemplifyingExample(s) and Comparative(s). However, the invention is not limited bythe description of Example(s).

Note that solid-property values of each material, which are shown in theTable 2 below, were measured in the following manner.

The Eg(T) was defined based on phosphorescence spectrum.

Specifically, each material was dissolved in an EPA solvent(diethylether:isopentane:ethanol=5:5:2 in volume ratio) at aconcentration of 10 μmol/L, thereby forming a sample for phosphorescencemeasurement.

The sample for phosphorescence measurement was put into a quartz celland is cooled to 77 K.

Excitation light was irradiated to the sample and the wavelength ofemitted phosphorescence was measured.

A tangent line was drawn to be tangent to a rising section adjacent toshort-wavelength of the obtained phosphorescence spectrum, a wavelengthvalue at an intersection of the tangent line and a base line obtainedfrom absorbance was obtained.

The value of the obtained wavelength value converted into energy wasdefined as the Eg(T).

For the measurement, a commercially-available measuring equipment F-4500(manufactured by Hitachi, Ltd.) was used.

The affinity level Af (electron affinity) means energy emitted orabsorbed when an electron is fed to a molecule of a material. Theaffinity level is defined as “positive” when energy is emitted whilebeing defined as “negative” when energy is absorbed.

The affinity level Af is defined by an ionization potential Ip and anoptical energy gap Eg(S) as follows.Af=Ip−Eg(S)

Here, the ionization potential Ip refers to energy necessary for acompound of each material to remove electrons to ionize, for which avalue measured with an ultraviolet ray photoelectron spectrometer (AC-3manufactured by Riken Keiki Co., Ltd.).

The optical energy gap Eg(S) refers to a difference between a conductionlevel and a valence electron level. For instance, Eg(S) is a valueobtained by converting into energy a wavelength value at an intersectionof a long-wavelength-side tangent line in an absorbing spectrum of atoluene-diluted solution of each material and a base line in theabsorbing spectrum obtained according to absorbance.

Example 1

A glass substrate (size: 25 mm×75 mm×1.1 mm thick) having an ITOtransparent electrode (manufactured by Geomatec Co., Ltd.) wasultrasonic-cleaned in isopropyl alcohol for five minutes, and thenUV/ozone-cleaned for 30 minutes.

After the glass substrate having the transparent electrode line wascleaned, the glass substrate was mounted on a substrate holder of avacuum deposition apparatus. Then, 50-nm thick film of4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (hereinafter abbreviatedas “NPD film”) was initially formed by resistance heating depositiononto a surface of the glass substrate where the transparent electrodeline was provided so that the NPD film covered the transparentelectrode. The NPD film served as the hole injecting/transporting layer.

A 40-nm thick film of the following compounds F and E, which were usedas the first and second hosts, was formed on the NPD film by resistanceheating deposition. The deposited mass of the compound E occupied 20%(mass ratio) of the entire host consisting of the first host and thesecond host. Simultaneously with the deposition of the host, Ir(piq)₃,which was used as the phosphorescent dopant, was deposited to becontained at a content of 5% (mass ratio) of the host. This film servedas the phosphorescent-emitting layer.

Subsequently, a 40-nm thick film of a compound J was formed on thephosphorescent-emitting layer. This film served as an electron injectinglayer.

After that, LiF was formed into 1-nm thick film. Metal (Al) wasdeposited on the LiF film to form a 150-nm thick metal cathode, therebyproviding the organic electroluminescence device.

Examples 2 to 16 and Comparatives 1 to 6

The organic electroluminescence device was manufactured in the samemanner as in Example 1 except that the compounds constituting the hostwere altered as in the following Table.

TABLE 1 First Host Second Host Example 1 Compound F (80 wt. %) CompoundE (20 wt. %) Example 2 Compound F (50 wt. %) Compound E (50 wt. %)Example 3 Compound F (20 wt. %) Compound E (80 wt. %) Example 4 CompoundF (80 wt. %) Compound D (20 wt. %) Example 5 Compound F (50 wt. %)Compound D (50 wt. %) Example 6 Compound F (20 wt. %) Compound D (80 wt.%) Example 7 Compound D (80 wt. %) Compound E (20 wt. %) Example 8Compound D (50 wt. %) Compound E (50 wt. %) Example 9 Compound D (20 wt.%) Compound E (80 wt. %) Example 10 Compound G (80 wt. %) Compound E (20wt. %) Example 11 Compound G (50 wt. %) Compound E (50 wt. %) Example 12Compound G (20 wt. %) Compound E (80 wt. %) Example 13 Compound F (80wt. %) BALq (20 wt. %) Example 14 Compound F (20 wt. %) Zn (BTP)₂ (80wt. %) Example 15 Compound D (20 wt. %) BALq (20 wt. %) Example 16Compound D (80 wt. %) Zn (BTP)₂ (80 wt. %) Comparative 1 Compound D —Comparative 2 Compound E — Comparative 3 Compound F — Comparative 4Compound G — Comparative 5 BAlq — Comparative 6 Zn (BTP)₂ — (Contentrelative to the entire host)

[Evaluation of Organic EL Device]

The organic electroluminecence devices each manufactured as describedabove were driven by direct-current electricity (1 mA/cm²) to emitlight, and then the luminance (L) and voltage were measured.

Based on the measurement, the current efficiency (L/J) was obtained. Inaddition, by conducting a direct-current continuous current test withthe initial luminance intensity being set at 5000 nit(cd/m²) for eachorganic electroluminescence device, time elapsed until the initialluminance intensity was reduced to the half (i.e., time until half-life)was measured for each organic electroluminescence device.

The results are shown in the following Table 2. The affinity level (Af)and the triplet energy gap (Eg(T)) of the respective materials are shownin the following Table 3.

TABLE 2 Voltage Luminous Efficiency Emission Lifetime (V) (L/J) (cd/A)(H, @ 5000 nit) Example 1 4.25  9.9 3000 Example 2 4.30 10.2 3000Example 3 4.33 11.5 4000 Example 4 4.36 11.0 5000 Example 5 4.35 10.54000 Example 6 4.28 10.3 3000 Example 7 4.32 11.8 3000 Example 8 4.3411.6 4000 Example 9 4.35 11.9 6000 Example 10 4.61 11.3 3000 Example 114.42 10.8 3000 Example 12 4.35 10.5 4000 Example 13 4.80 11.5 2500Example 14 4.32 11.7 2000 Example 15 5.01 10.9 1500 Example 16 4.54  9.81400 Comparative 1 3.92  9.4  500 Comparative 2 4.31 11.8 1000Comparative 3 4.42 11.7 1000 Comparative 4 5.13 11.3  800 Comparative 55.74 10.8  700 Comparative 6 3.83 10.5  200

TABLE 3 Af Eg(T) (eV) (eV) Compound D 2.64 2.38 Compound E 2.8  2.40Compound F 2.55 2.44 Compound G 2.66 2.66

As is clear from the Tables 1 and 2, the organic electroluminescencedevice according to Examples 1 to 16 containing the second host inaddition to the first host exhibited a longer lifetime than the organicelectroluminescence device according to Comparatives 1 to 6 notcontaining the second host.

Accordingly, it is recognized that the organic electroluminescencedevice of the invention provides a longer lifetime than a typicalphosphorescent organic electroluminescence device in which the secondhost is not added.

In Examples 1 to 6, the compound E or the compound D is added as thesecond host to Comparative 3 containing the compound F as the sole host.Consequently, the drive voltage of the organic electroluminescencedevice is reduced to lengthen the lifetime.

In Examples 7 to 9, the compound E is added as the second host toComparative 1 containing the compound D as the sole host. Consequently,the efficiency of the organic electroluminescence device is enhanced andthe lifetime is lengthened.

In Examples 10 to 12, the compound E is added as the second host toComparative 4 containing the compound G as the sole host. Consequently,the drive voltage of the organic electroluminescence device is reducedto lengthen the lifetime.

In Examples 13 to 16, the compound F or the compound D is added toComparative 5 containing BAlq as the sole host or Comparative 6containing An(BTP)₂ as the sole host. Consequently, the lifetime of theorganic electroluminescence device is lengthened.

It should be noted that the invention is not limited to the abovedescription but may include any modification as long as suchmodification stays within a scope of the invention.

For instance, the following is a preferable example of such modificationmade to the present invention.

According to the aspect of the present invention, thephosphorescent-emitting layer may preferably contain an assistancesubstance for assisting injection of charges.

When the phosphorescent-emitting layer is formed of a host material thatexhibits a large Eg(T), a difference in Ip between the host material andthe hole injecting/transporting layer etc. becomes so large that theholes can hardly be injected into the phosphorescent-emitting layer anda driving voltage required for providing sufficient luminance may beraised.

In the above instance, introducing a hole-injectable orhole-transportable assistance substance for assisting injection ofcharges in the phosphorescent-emitting layer can contribute tofacilitation of the injection of the holes into thephosphorescent-emitting layer and to reduction of the driving voltage.

As the assistance material for assisting the injection of charges, forinstance, a typical hole injecting/transporting material or the like canbe used.

Examples of the material are a triazole derivative (see, for instance,the specification of U.S. Pat. No. 3,112,197), an oxadiazole derivative(see, for instance, the specification of U.S. Pat. No. 3,189,447), animidazole derivative (see, for instance, JP-B-37-16096), apolyarylalkane derivative (see, for instance, the specifications of U.S.Pat. No. 3,615,402, U.S. Pat. No. 3,820,989 and U.S. Pat. No. 3,542,544,JP-B-45-555, JP-B-51-10983, JP-A-51-93224, JP-A-55-17105, JP-A-56-4148,JP-A-55-108667, JP-A-55-156953, and JP-A-56-36656), a pyrazolinederivative and a pyrazolone derivative (see, for instance, thespecifications of U.S. Pat. No. 3,180,729 and U.S. Pat. No. 4,278,746,JP-A-55-88064, JP-A-55-88065, JP-49-105537, JP-A-55-51086,JP-A-56-80051, JP-A-56-88141, JP-A-57-45545, JP-A-54-112637 andJP-A-55-74546), a phenylenediamine derivative (see, for instance, thespecification of U.S. Pat. No. 3,615,404, JP-B-51-10105, JP-B-46-3712,JP-B-47-25336, JP-A-54-53435, JP-A-54-110536 and JP-A-54-119925), anarylamine derivative (see, for instance, the specifications of U.S. Pat.No. 3,567,450, U.S. Pat. No. 3,180,703, U.S. Pat. No. 3,240,597, U.S.Pat. No. 3,658,520, U.S. Pat. No. 4,232,103, U.S. Pat. No. 4,175,961 andU.S. Pat. No. 4,012,376, JP-B-49-35702, JP-B-39-27577, JP-A-55-144250,JP-A-56-119132 and JP-A-56-22437 and the specification of West GermanyPatent No. 1,110,518), an amino-substituted chalcone derivative (see,for instance, the specification of U.S. Pat. No. 3,526,501), an oxazolederivative (disclosed in, for instance, the specification of U.S. Pat.No. 3,257,203), a styrylanthracene derivative (see, for instance,JP-A-56-46234), a fluorenone derivative (see, for instance,JP-A-54-110837), a hydrazone derivative (see, for instance, thespecification of U.S. Pat. No. 3,717,462 and JP-A-54-59143,JP-A-55-52063, JP-A-55-52064, JP-A-55-46760, JP-A-55-85495,JP-A-57-11350, JP-A-57-148749 and JP-A-02-311591), a stilbene derivative(see, for instance, JP-A-61-210363, JP-A-61-228451, JP-A-61-14642,JP-A-61-72255, JP-A-62-47646, JP-A-62-36674, JP-A-62-10652,JP-A-62-30255, JP-A-60-93455, JP-A-60-94462, JP-A-60-174749 andJP-A-60-175052), a silazane derivative (see the specification of U.S.Pat. No. 4,950,950), a polysilane type (see JP-A-02-204996), ananiline-based copolymer (see JP-A-02-282263), and a conductive polymeroligomer (particularly, thiophene oligomer) disclosed in JP-A-01-211399.

The hole-injectable material, examples of which are as listed above, ispreferably a porphyrin compound (disclosed in JP-A-63-295695 etc.), anaromatic tertiary amine compound or a styrylamine compound (see, forinstance, the specification of U.S. Pat. No. 4,127,412, JP-A-53-27033,JP-A-54-58445, JP-A-54-149634, JP-A-54-64299, JP-A-55-79450,JP-A-55-144250, JP-A-56-119132, JP-A-61-295558, JP-A-61-98353 orJP-A-63-295695), particularly preferably an aromatic tertiary aminecompound.

In addition, 4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl(hereinafter, abbreviated as NPD) having in the molecule two fusedaromatic rings disclosed in U.S. Pat. No. 5,061,569,4,4′,4″-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine(hereinafter, abbreviated as MTDATA) in which three triphenylamine unitsdisclosed in JP-A-04-308688 are bonded in a starbust form and the likemay also be used.

Further, a hexaazatriphenylene derivative disclosed in Japanese PatentNo. 3614405 and No. 3571977 and U.S. Pat. No. 4,780,536 may alsopreferably be used as the hole-injecting material.

Alternatively, inorganic compounds such as p-type Si and p-type SiC canalso be used as the hole-injecting material.

The invention claimed is:
 1. An organic electroluminescence device,comprising: an anode; a cathode; and an organic thin-film layerinterposed between the anode and the cathode, wherein the organicthin-film layer includes a phosphorescent-emitting layer containing ahost and a phosphorescent dopant, the host contains a first host and asecond host, one of the first host and the second host exhibits a higheraffinity level than the other, the first host includes a substituted orunsubstituted polycyclic fused aromatic skeleton, the skeleton having 10to 30 ring-forming atoms not including an atom of a substituent, aminimum excited triplet energy gap of the first host is in a range from2.1 eV to 2.7 eV.
 2. The organic electroluminescence device according toclaim 1, wherein the polycyclic fused aromatic skeleton is present in achemical structure formula as a divalent or multivalent group.
 3. Theorganic electroluminescence device according to claim 1, wherein thepolycyclic fused aromatic skeleton comprises the substituent, and thesubstituent is a substituted or unsubstituted aryl or heteroaryl group.4. The organic electroluminescence device according to claim 3, whereinthe substituent does not have a carbazole skeleton.
 5. The organicelectroluminescence device according to claim 2, wherein the polycyclicfused aromatic skeleton is selected from the group consisting of asubstituted or unsubstituted phenanthrene-diyl, chrysene-diyl,fluoranthene-diyl and triphenylene-diyl.
 6. The organicelectroluminescence device according to claim 5, wherein the polycyclicfused aromatic skeleton is substituted by a group includingphenanthrene, chrysene, fluoranthene and triphenylene.
 7. The organicelectroluminescence device according to claim 1, wherein the polycyclicfused aromatic skeleton is represented by any one of formulae (1) to (4)as follows,

where Ar¹ to Ar⁵ in the formulae (1) to (4) each represent a substitutedor unsubstituted fused cyclic structure having 4 to 10 ring-formingcarbon atoms not including the atom of the substituent.
 8. The organicelectroluminescence device according to claim 1, wherein the first hostis a substituted or unsubstituted phenanthrene or a substituted orunsubstituted chrysene.
 9. The organic electroluminescence deviceaccording to claim 1, wherein the second host comprises the polycyclicfused aromatic skeleton.
 10. The organic electroluminescence deviceaccording to claim 9, wherein the second host is a substituted orunsubstituted phenanthrene or a substituted or unsubstituted chrysene.11. The organic electroluminescence device according to claim 1, whereinthe first host comprises the polycyclic fused aromatic skeleton, anaffinity level of the second host is higher than the affinity level ofthe first host, and a content of the second host in the host is in arange from 1 mass % to 50 mass %.
 12. The organic electroluminescencedevice according to claim 1, wherein the phosphorescent dopant containsa metal complex having: a metal selected from the group consisting ofIr, Pt, Os, Au, Cu, Re and Ru; and a ligand.
 13. The organicelectroluminescence device according to claim 1, wherein a wavelength ofa light of a maximum luminance of the phosphorescent dopant is in arange from 500 nm to 700 nm.
 14. The organic electroluminescence deviceaccording to claim 1, wherein the organic thin-film layer comprises anelectron injecting layer between the cathode and thephosphorescent-emitting layer, and the electron injecting layer containsa nitrogen-containing heterocyclic derivative.
 15. The organicelectroluminescence device according to claim 1, wherein areduction-causing dopant is present at an interfacial region between thecathode and the organic thin-film layer.
 16. Anorganic-electroluminescent-material-containing solution for preparing aphosphorescent-emitting layer comprising: a host; a phosphorescentdopant; and a solvent in which the host and the phosphorescent dopantare dissolved, wherein the host contains a first host and a second host,one of the first host and the second host exhibits a higher affinitylevel than the other, the first host includes a substituted orunsubstituted polycyclic fused aromatic skeleton, the skeleton having 10to 30 ring-forming atoms not including an atom of a substituent, and aminimum excited triplet energy gap of the first host is in a range from2.1 eV to 2.7 eV.